Self-decodability for low-density parity-check codes

ABSTRACT

A technique for hybrid automatic repeat request (HARD) transmissions using low-density parity-check (LDPC) coding with self-decodable retransmissions is disclosed. Data is encoded using a low-density parity check code to obtain encoded data, where the encoded data includes core data and non-core data. The encoded data is then stored in a buffer for transmission. A plurality of redundancy versions of the encoded data is then transmitted, wherein all redundancy versions of encoded data include core data, and each of the transmitted redundancy versions of the encoded data includes at least a different subset of the core data. The core data may be reordered prior to obtaining at least one of the different subsets of core data. Each of the transmitted redundancy versions of the encoded data includes sufficient core data to permit self-decodability of the transmission at a receiver.

CROSS REFERENCE TO RELATED APPLICATIONS

The present Application for Patent claims priority to U.S. ProvisionalApplication No. 62/681,975 filed Jun. 7, 2018, which is hereby expresslyincorporated by reference.

FIELD OF THE INVENTION

The present disclosure relates to error correcting codes forcommunications, and more particularly, to methods and apparatus, forusing low-density parity-check codes with self-decodability.

BACKGROUND

Wireless communication networks are widely deployed to provide variouscommunication services such as voice, video, packet data, messaging,broadcast, etc. These wireless networks may be multiple-access networkscapable of supporting multiple users by sharing the available networkresources. Examples of such multiple-access networks include CodeDivision Multiple Access (CDMA) networks, Time Division Multiple Access(TDMA) networks, Frequency Division Multiple Access (FDMA) networks,Orthogonal FDMA (OFDMA) networks, and Single-Carrier FDMA (SC-FDMA)networks.

As the use of mobile wireless devices, such as smart phones and tabletdevices, becomes more ubiquitous, the demands on the limited amount ofradio frequency spectrum used by those devices has increased, resultingin wireless network congestion and reduced bandwidth for devicesoperating in the licensed spectrum. A variety of techniques have beenintroduced to provide improve the effective data throughput, includingcoding and error correction. Furthermore, techniques for encoding andmodulating data can improve efficient usage of bandwidth as well asenable reliable decoding or error detection at a receiver.

SUMMARY

A method and apparatus are provided for wireless communication at atransmitter. Data may be encoded using a low-density parity check codeto obtain encoded data, where the encoded data includes core data andnon-core data. The encoded data may then be stored in a buffer (e.g., acircular buffer) for transmission. The non-core data may include paritydata for forward error correction. The low-density parity check code mayuse a quasi-cyclic lifting structure. The quasi-cyclic lifting structuremay be a sparse bipartite graph having a core part that is more denselypopulated than a non-core part.

A plurality of redundancy versions of the encoded data may then betransmitted, wherein all redundancy versions of encoded data includecore data, and each of the transmitted redundancy versions of theencoded data includes at least a different subset of the core data. Eachof the transmitted redundancy versions of the encoded data may includesufficient core data to permit self-decodability of the transmission ata receiver. The core data may be reordered prior to obtaining at leastone of the different subsets of core data.

In one example, a transmission of a first redundancy version of theencoded data includes all of the core data, while a transmission of asecond redundancy version of the encoded data includes fewer than all ofthe core data.

According to one aspect, the plurality of redundancy versions may beselected from a set of redundancy versions, where the set of redundancyversions and their transmission order is preconfigured, and wherein eachof the set of redundancy versions includes sufficient core data topermit self-decodability. In some instances, each of the set ofredundancy versions may have a first starting point for the core dataand a second starting point for the non-core data, which are known tothe intended receiver.

In some examples, transmitting a plurality of redundancy versions of theencoded data may include: (a) transmitting a first redundancy version ofthe encoded data, wherein the first redundancy version of the encodeddata includes at least a first subset of the core data; (b) transmittinga second redundancy version of the encoded data, wherein the secondredundancy version of the encoded data includes at least a second subsetof the core data different from the first subset of core data, and wherethe core data is reordered prior to obtaining the second subset of coredata; and/or (c) transmitting a third redundancy version of the encodeddata, wherein the third redundancy version of the encoded data includesat least a third subset of the core data different from the first andsecond subsets of core data, and the same reordered core data is used toobtain the second and third subsets of core data. In someimplementations, the first subset of the core data may include all thecore data. The second subset of the core data may include fewer than allthe core data. The second redundancy version of the encoded data mayinclude more non-core data than the first redundancy version of theencoded data. The second redundancy version of the encoded data may betransmitted upon receipt of an indicator to retransmit the encoded data.In another example, the first redundancy version of the encoded data hasa higher transmission rate for the data than the second redundancyversion of the encoded data.

A method operational and apparatus are provided for wirelesscommunication at a receiver. A plurality of redundancy versions ofencoded data may be received, where the encoded data includes core dataand non-core data, wherein each of the received redundancy versions ofthe encoded data includes at least a different subset of the core data.The non-core data may include parity data for forward error correction.The encoded data may be obtained from one or more of the plurality ofredundancy versions of encoded data. For instance, the encoded data maybe obtained by combining likelihood ratios for the received plurality ofredundancy versions of the encoded data. The plurality of redundancyversions may be selected from a set of redundancy versions, where theset of redundancy versions and their transmission order is pre-arrangedwith a transmitter.

In one example, each of the received redundancy versions of the encodeddata includes sufficient core data to permit self-decodability of theencoded data.

The encoded data may then be decoded using a low-density parity checkcode to obtain decoded data. The low-density parity check code may use aquasi-cyclic lifting structure. The quasi-cyclic lifting structure maybe a sparse bipartite graph having a core part that is more denselypopulated than a non-core part.

In one example, each of the set of redundancy versions may have a firststarting point for the core data and a second starting point for thenon-core data, which are provided to the receiver.

In some implementations, a first redundancy version of the encoded datamay include all of the core data, while a second redundancy version ofthe encoded data may include less than all the core data.

In another example, receiving a plurality of redundancy versions of theencoded data may include: (a) receiving a first redundancy version ofthe encoded data, wherein the first redundancy version of the encodeddata includes at least a first subset of the core data; (b) receiving asecond redundancy version of the encoded data, wherein the secondredundancy version of the encoded data includes at least a second subsetof the core data different from the first subset of core data, and wherethe second subset of core data is based on a reordered version of thecore data relative to the first subset of core data; and/or (c)receiving a third redundancy version of the encoded data, wherein thethird redundancy version of the encoded data includes at least a thirdsubset of the core data different from the first and second subsets ofcore data, and the second subset and third subset of core data is basedon the same reordered core data. In various examples, the first subsetof the core data may include all the core data, and the second subset ofthe core data may include fewer than all the core data. The secondredundancy version of the encoded data may include more non-core datathan the first redundancy version of the encoded data. The receiver maysend an indicator to retransmit the encoded data prior to receiving thesecond redundancy version of the encoded data. In some instances, ablock length of the second redundancy version of the encoded data isdifferent than first redundancy version of the encoded data. In otherinstances, a block length of the second redundancy version of theencoded data is the same as first redundancy version of the encodeddata.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a wireless communication system.

FIG. 2 illustrates an example of a schematic of a radio access network(RAN).

FIG. 3 illustrates an example block diagram of a base station and aplurality of user equipment (UEs).

FIG. 4 illustrates a schematic of an example of an Orthogonal FrequencyDivision Multiplexing (OFDM) waveform frame structure.

FIG. 5 is an example matrix illustrating a 5G new radio (NR) low-densityparity-check (LDPC) code structure using a sparse bipartite graphcomprising a systematic part and a parity part.

FIG. 6 is a block diagram illustrating an example of a hybrid automaticrepeat request (HARQ) transmission process using a low-densityparity-check (LDPC) code.

FIG. 7 illustrates an example of a circular buffer and redundancyversion order for a HARQ transmission.

FIG. 8 is a block diagram illustrating a HARQ transmission process tofacilitate self-decodability.

FIG. 9 illustrates an example of how encoded bits, such as those withina circular buffer, may be reordered for or during a retransmission.

FIG. 10 illustrates HARQ transmissions using low-density parity-check(LDPC) coding and reordering of a circular buffer duringretransmissions.

FIG. 11 is a block diagram illustrating an example of a bit encoding andtransmission circuit.

FIG. 12 is a block diagram of an example of a communication apparatusconfigured to send HARQ transmissions using LDPC coding while reorderinga buffer for retransmissions.

FIG. 13 illustrates an example of a method for HARQ transmissions usingLDPC coding and reordering of a buffer during retransmissions.

FIG. 14 is a block diagram illustrating an example of a receiver anddata decoding circuit.

FIG. 15 is a block diagram of an example of a communication apparatusconfigured to perform HARQ reception using a modified LDPC coding.

FIG. 16 is a block diagram illustrating an example of a method forreceiving HARQ transmissions using LDPC coding with reorderedretransmissions.

DETAILED DESCRIPTION OF THE INVENTION

The detailed description set forth below in connection with the appendeddrawings is intended as a description of various configurations and isnot intended to represent the only configurations in which the conceptsdescribed herein may be practiced. The detailed description includesspecific details for the purpose of providing a thorough understandingof various concepts. However, it will be apparent to those skilled inthe art that these concepts may be practiced without these specificdetails. In some instances, well known structures and components areshown in block diagram form in order to avoid obscuring such concepts.

Various aspects of the disclosure are described below. It should beapparent that the teachings herein may be embodied in a wide variety offorms and that any specific structure, function, or both being disclosedherein is merely representative. Based on the teachings herein oneskilled in the art should appreciate that an aspect disclosed herein maybe implemented independently of any other aspects and that two or moreof these aspects may be combined in various ways. For example, anapparatus may be implemented or a method may be practiced using anynumber of the aspects set forth herein. In addition, such an apparatusmay be implemented or such a method may be practiced using otherstructure, functionality, or structure and functionality in addition toor other than one or more of the aspects set forth herein. Furthermore,an aspect may comprise at least one element of a claim.

The techniques described herein may be applied to various broadbandwireless communication systems, including communication systems that arebased on an orthogonal multiplexing scheme. Examples of suchcommunication systems include Spatial Division Multiple Access (SDMA)system, Time Division Multiple Access (TDMA) system, OrthogonalFrequency Division Multiple Access (OFDMA) system, and Single-CarrierFrequency Division Multiple Access (SC-FDMA) system. An SDMA system mayutilize sufficiently different directions to simultaneously transmitdata belonging to multiple user terminals. A TDMA system may allowmultiple user terminals to share the same frequency channel by dividingthe transmission signal into different time slots, each time slot beingassigned to different user terminal Δn OFDMA system utilizes orthogonalfrequency division multiplexing (OFDM), which is a modulation techniquethat partitions the overall system bandwidth into multiple orthogonalsub-carriers. These sub-carriers may also be called tones, bins, etc.With OFDM, each sub-carrier may be independently modulated with data. AnSC-FDMA system may utilize interleaved FDMA (IFDMA) to transmit onsub-carriers that are distributed across the system bandwidth, localizedFDMA (LFDMA) to transmit on a block of adjacent sub-carriers, orenhanced FDMA (EFDMA) to transmit on multiple blocks of adjacentsub-carriers. In general, modulation symbols are sent in the frequencydomain with OFDM and in the time domain with SC-FDMA.

The teachings herein may be incorporated into (e.g., implemented withinor performed by) a variety of wired or wireless apparatuses (e.g.,nodes). In some aspects, a wireless node implemented in accordance withthe teachings herein may be an access point or an access terminal.

FIG. 1 illustrates an example of a wireless communication system 100.The wireless communication system 100 includes three interactingdomains: a core network 102, a radio access network (RAN) 104, and auser equipment (UE) 106. By virtue of the wireless communication system100, the UE 106 may be enabled to carry out data communication with anexternal data network 110, such as (but not limited to) the Internet.

The RAN 104 may implement any suitable wireless communication technologyor technologies to provide radio access to the UE 106. As one example,the RAN 104 may operate according to 3rd Generation Partnership Project(3GPP) New Radio (NR) specifications, often referred to as 5G. Asanother example, the RAN 104 may operate under a hybrid of 5G NR andEvolved Universal Terrestrial Radio Access Network (eUTRAN) standards,often referred to as LTE. The 3GPP refers to this hybrid RAN as anext-generation RAN (NG-RAN). Of course, many other examples may beutilized, and are contemplated, within the scope of the presentdisclosure.

As illustrated, the RAN 104 includes a plurality of base stations 108.Broadly, a base station is a network element in a radio access networkresponsible for radio transmission and reception in one or more cells toor from a UE. In different technologies, standards, or contexts, a basestation may variously be referred to by those skilled in the art as abase transceiver station (BTS), a radio base station, a radiotransceiver, a transceiver function, a basic service set (BSS), anextended service set (ESS), an access point (AP), a Node B (NB), aneNode B (eNB), a gNode B (gNB), or some other suitable terminology.

The radio access network 104 is further illustrated supporting wirelesscommunication for multiple mobile apparatuses. A mobile apparatus may bereferred to as user equipment (UE) in 3GPP standards, but may also bereferred to by those skilled in the art as a mobile station (MS), asubscriber station, a mobile unit, a subscriber unit, a wireless unit, aremote unit, a mobile device, a wireless device, a wirelesscommunications device, a remote device, a mobile subscriber station, anaccess terminal (AT), a mobile terminal, a wireless terminal, a remoteterminal, a handset, a terminal, a user agent, a mobile client, aclient, or some other suitable terminology. A UE may be an apparatusthat provides a user with access to network services.

Within the present document, a “mobile” apparatus need not necessarilyhave a capability to move, and may be stationary. The term mobileapparatus or mobile device broadly refers to a diverse array of devicesand technologies. For example, some non-limiting examples of a mobileapparatus include a mobile, a cellular (cell) phone, a smart phone, asession initiation protocol (SIP) phone, a laptop, a personal computer(PC), a notebook, a netbook, a smartbook, a tablet, a personal digitalassistant (PDA), and a broad array of embedded systems, e.g.,corresponding to an “Internet of things” (IoT). A mobile apparatus mayadditionally be an automotive or other transportation vehicle, a remotesensor or actuator, a robot or robotics device, a satellite radio, aglobal positioning system (GPS) device, an object tracking device, adrone, a multi-copter, a quad-copter, a remote control device, aconsumer and/or wearable device, such as eyewear, a wearable camera, avirtual reality device, a smart watch, a health or fitness tracker, adigital audio player (e.g., MP3 player), a camera, a game console, etc.A mobile apparatus may additionally be a digital home or smart homedevice such as a home audio, video, and/or multimedia device, anappliance, a vending machine, intelligent lighting, a home securitysystem, a smart meter, etc. A mobile apparatus may additionally be asmart energy device, a security device, a solar panel or solar array, amunicipal infrastructure device controlling electric power (e.g., asmart grid), lighting, water, etc.; an industrial automation andenterprise device; a logistics controller; agricultural equipment;military defense equipment, vehicles, aircraft, ships, and weaponry,etc. Still further, a mobile apparatus may provide for connectedmedicine or telemedicine support, i.e., health care at a distance.Telehealth devices may include telehealth monitoring devices andtelehealth administration devices, whose communication may be givenpreferential treatment or prioritized access over other types ofinformation, e.g., in terms of prioritized access for transport ofcritical service data, and/or relevant QoS for transport of criticalservice data.

Wireless communication between a RAN 104 and a UE 106 may be describedas utilizing an air interface. Transmissions over the air interface froma base station (e.g., base station 108) to one or more UEs (e.g., UE106) may be referred to as downlink (DL) transmission. In accordancewith certain aspects of the present disclosure, the term downlink mayrefer to a point-to-multipoint transmission originating at a schedulingentity (described further below; e.g., base station 108). Another way todescribe this scheme may be to use the term broadcast channelmultiplexing. Transmissions from a UE (e.g., UE 106) to a base station(e.g., base station 108) may be referred to as uplink (UL)transmissions. In accordance with further aspects of the presentdisclosure, the term uplink may refer to a point-to-point transmissionoriginating at a scheduled entity (described further below; e.g., UE106).

In some examples, access to the air interface may be scheduled, whereina scheduling entity (e.g., a base station 108) allocates resources forcommunication among some or all devices and equipment within its servicearea or cell. Within the present disclosure, as discussed further below,the scheduling entity may be responsible for scheduling, assigning,reconfiguring, and releasing resources for one or more scheduledentities. That is, for scheduled communication, UEs 106, which may bescheduled entities, may utilize resources allocated by the schedulingentity (e.g., base station 108).

Base stations 108 are not the only entities that may function asscheduling entities. That is, in some examples, a UE may function as ascheduling entity, scheduling resources for one or more other UEs (e.g.,one or more scheduled entities).

As illustrated in FIG. 1, a scheduling entity (e.g., base stations 108)may broadcast downlink traffic 112 to one or more scheduled entities(e.g., UE 106). Broadly, the scheduling entity (e.g., base stations 108)is a node or device responsible for scheduling traffic in a wirelesscommunication network, including the downlink traffic 112 and, in someexamples, uplink traffic 116 from one or more scheduled entities (e.g.,UE 106) to the scheduling entity (e.g., base station 108). On the otherhand, the scheduled entity (e.g., UE 106) is a node or device thatreceives downlink control information 114, including but not limited toscheduling information (e.g., a grant), synchronization or timinginformation, or other control information from another entity in thewireless communication network such as the scheduling entity (e.g., basestation 108).

In general, base stations 108 may include a backhaul interface forcommunication with a backhaul portion 120 of the wireless communicationsystem. The backhaul 120 may provide a link between a base station 108and the core network 102. Further, in some examples, a backhaul networkmay provide interconnection between the respective base stations 108.Various types of backhaul interfaces may be employed, such as a directphysical connection, a virtual network, or the like using any suitabletransport network.

The core network 102 may be a part of the wireless communication system100, and may be independent of the radio access technology used in theRAN 104. In some examples, the core network 102 may be configuredaccording to 5G standards (e.g., 5GC). In other examples, the corenetwork 102 may be configured according to a 4G evolved packet core(EPC), or any other suitable standard or configuration. 5G NR willoperate across many radio frequency bands. The frequency bands includelow bands (e.g., below 1 GHz) for long range in cooperation with mobilebroadband and massive Internet of Things (IoT) operations. The low bandsinclude spectrum bands around 600 MHz, 700 MHz, 850/900 MHz, forexample. The frequency bands also include mid-bands that provide widerbandwidths than the low bands in cooperation with enhanced Mobile BroadBand (eMBB) and mission-critical operations. The mid-bands include, forexample, spectrum between 1 to 6 GHz and include spectrum around 3.4-3.8GHz, 3.8-4.2 GHz, and 4.4-4.9 GHz, for example. The frequency bands alsoinclude high bands (mmWave bands) with extreme bandwidths in spectrumaround 24.25-27.5 GHz, 27.5.29.5, 37-40, 64-71 GHz, for example.

The 5G NR mmWave bands offer many advantages, and, as explained above,include disadvantages such as higher pathloss and/or susceptibility tointerference. Consequently, HARQ transmissions encoded by a low-densityparity-check (LDPC) code are used to improve throughput performance.

Communication of information, including the downlink traffic 112,downlink control 114, uplink traffic 116, and/or uplink control 118, mayinvolve encoding and decoding information to enable reliablecommunication and/or error correction induced by a wireless channel. Inone embodiment, LDPC codes are used to encode and decode data. In somecases, multiple transmissions corresponding to a specific transportblock or other unit of information may be sent to allow the informationto be received and decoded. For example, a hybrid automatic repeatrequest scheme may be used to send redundant transmissions correspondingto the same information (which may be referred to as redundancyversions). As discussed herein, each redundancy version sent by atransmitter (e.g., a UE 106 or a base station 108) may includeself-decodable such that it is possible that a receiver (e.g., a UE 106or a base station 108) can decode the full message based on any singleredundancy version.

FIG. 2 illustrates an example of a schematic of a radio access network(RAN) 200. In some examples, the RAN 200 may be the same as the RAN 104described above and illustrated in FIG. 1. The geographic area coveredby the RAN 200 may be divided into cellular regions (cells) that can beuniquely identified by a user equipment (UE) based on an identificationbroadcasted from one access point or base station. FIG. 2 illustratesmacrocells 202, 204, and 206, and a small cell 208, each of which mayinclude one or more sectors (not shown). A sector is a sub-area of acell. All sectors within one cell are served by the same base station. Aradio link within a sector can be identified by a single logicalidentification belonging to that sector. In a cell that is divided intosectors, the multiple sectors within a cell can be formed by groups ofantennas with each antenna responsible for communication with UEs in aportion of the cell.

In FIG. 2, two base stations 210 and 212 are shown in cells 202 and 204;and a third base station 214 is shown controlling a remote radio head(RRH) 216 in cell 206. That is, a base station can have an integratedantenna or can be connected to an antenna or RRH by feeder cables. Inthe illustrated example, the cells 202, 204, and 126 may be referred toas macrocells, as the base stations 210, 212, and 214 support cellshaving a large size. Further, a base station 218 is shown in the smallcell 208 (e.g., a microcell, picocell, femtocell, home base station,home Node B, home eNode B, etc.) which may overlap with one or moremacrocells. In this example, the cell 208 may be referred to as a smallcell, as the base station 218 supports a cell having a relatively smallsize. Cell sizing can be done according to system design as well ascomponent constraints.

It is to be understood that the radio access network 200 may include anynumber of wireless base stations and cells. Further, a relay node may bedeployed to extend the size or coverage area of a given cell. The basestations 210, 212, 214, 218 provide wireless access points to a corenetwork for any number of mobile apparatuses. In some examples, the basestations 210, 212, 214, and/or 218 may be the same as the base station108 (e.g., scheduling entity) described above and illustrated in FIG. 1.

FIG. 2 further illustrates a quadcopter or drone 220, which may beconfigured to function as a base station. That is, in some examples, acell may not necessarily be stationary, and the geographic area of thecell may move according to the location of a mobile base station such asthe quadcopter 220.

Within the RAN 200, the cells may include UEs that may be incommunication with one or more sectors of each cell. Further, each basestation 210, 212, 214, 218, and 220 may be configured to provide anaccess point to a core network 102 (see FIG. 1) for all the UEs in therespective cells. For example, UEs 222 and 224 may be in communicationwith base station 210; UEs 226 and 228 may be in communication with basestation 212; UEs 230 and 232 may be in communication with base station214 by way of RRH 216; UE 234 may be in communication with base station218; and UE 236 may be in communication with mobile base station 220. Insome examples, the UEs 222, 224, 226, 228, 230, 232, 234, 236, 238, 240,and/or 242 may be the same as the UE 106 (e.g., scheduled entity)described above and illustrated in FIG. 1. In some examples, some of theUEs may be a vehicle or automobile (e.g., UE 224).

In some examples, a mobile network node (e.g., quadcopter 220 or vehicle224) may be configured to function as a UE. For example, the quadcopter220 may operate within cell 202 by communicating with base station 210.

In a further aspect of the RAN 200, sidelink signals may be used betweenUEs without necessarily relying on scheduling or control informationfrom a base station. For example, two or more UEs (e.g., UEs 226 and228) may communicate with each other using peer to peer (P2P) orsidelink signals 227 without relaying that communication through a basestation (e.g., base station 212). In a further example, UE 238 isillustrated communicating with UEs 240 and 242. Here, the UE 238 mayfunction as a scheduling entity or a primary sidelink device, and UEs240 and 242 may function as a scheduled entity or a non-primary (e.g.,secondary) sidelink device. In still another example, a UE may functionas a scheduling entity in a device-to-device (D2D), peer-to-peer (P2P),or vehicle-to-vehicle (V2V) network, and/or in a mesh network. In a meshnetwork example, UEs 240 and 242 may optionally communicate directlywith one another in addition to communicating with the scheduling entity238. Thus, in a wireless communication system with scheduled access totime-frequency resources and having a cellular configuration, a P2Pconfiguration, or a mesh configuration, a scheduling entity and one ormore scheduled entities may communicate utilizing the scheduledresources.

In the radio access network 200, the ability for a UE (e.g., vehicle224) to communicate while moving, independent of its location, isreferred to as mobility. The various physical channels between the UEand the radio access network are generally set up, maintained, andreleased under the control of an access and mobility management function(AMF, not illustrated, part of the core network 102 in FIG. 1), whichmay include a security context management function (SCMF) that managesthe security context for both the control plane and the user planefunctionality, and a security anchor function (SEAF) that performsauthentication.

In various aspects of the disclosure, a radio access network 200 mayutilize DL-based mobility or UL-based mobility to enable mobility andhandovers (i.e., the transfer of a UE's connection from one radiochannel to another or from one base station to another). In a networkconfigured for DL-based mobility, during a call with a schedulingentity, or at any other time, a UE may monitor various parameters of thesignal from its serving cell as well as various parameters ofneighboring cells. Depending on the quality of these parameters, the UEmay maintain communication with one or more of the neighboring cells.During this time, if the UE moves from one cell to another, or if signalquality from a neighboring cell exceeds that from the serving cell for agiven amount of time, the UE may undertake a handoff or handover fromthe serving cell to the neighboring (target) cell. For example, UE 224(illustrated as a vehicle, although any suitable form of UE may be used)may move from the geographic area corresponding to its serving cell 202to the geographic area corresponding to a neighbor cell 206. When thesignal strength or quality from the neighbor cell 206 exceeds that ofits serving cell 202 for a given amount of time, the UE 224 may transmita reporting message to its serving base station 210 indicating thiscondition. In response, the UE 224 may receive a handover command, andthe UE may undergo a handover to the cell 206.

In a network configured for UL-based mobility, UL reference signals fromeach UE may be utilized by the network to select a serving cell for eachUE. In some examples, the base stations 210, 212, and 214/216 maybroadcast unified synchronization signals (e.g., unified PrimarySynchronization Signals (PSSs), unified Secondary SynchronizationSignals (SSSs) and unified Physical Broadcast Channels (PBCH)). The UEs222, 224, 226, 228, 230, and 232 may receive the unified synchronizationsignals, derive the carrier frequency and slot timing from thesynchronization signals, and in response to deriving timing, transmit anuplink pilot or reference signal. The uplink pilot signal transmitted bya UE (e.g., UE 224) may be concurrently received by two or more cells(e.g., base stations 210 and 214/216) within the radio access network200. Each of the cells may measure a strength of the pilot signal, andthe radio access network (e.g., one or more of the base stations 210 and214/216 and/or a central node within the core network) may determine aserving cell for the UE 224. As the UE 224 moves through the radioaccess network 200, the network may continue to monitor the uplink pilotsignal transmitted by the UE 224. When the signal strength or quality ofthe pilot signal measured by a neighboring cell exceeds that of thesignal strength or quality measured by the serving cell, the network 200may handover the UE 224 from the serving cell to the neighboring cell,with or without informing the UE 224.

Although the synchronization signal transmitted by the base stations210, 212, and 214/216 may be unified, the synchronization signal may notidentify a particular cell, but rather may identify a zone of multiplecells operating on the same frequency and/or with the same timing. Theuse of zones in 5G networks or other next generation communicationnetworks enables the uplink-based mobility framework and improves theefficiency of both the UE and the network, since the number of mobilitymessages that need to be exchanged between the UE and the network may bereduced.

In various implementations, the air interface in the radio accessnetwork 200 may utilize licensed spectrum, unlicensed spectrum, orshared spectrum. Licensed spectrum provides for exclusive use of aportion of the spectrum, generally by virtue of a mobile networkoperator purchasing a license from a government regulatory body.Unlicensed spectrum provides for shared use of a portion of the spectrumwithout need for a government-granted license. While compliance withsome technical rules is generally still required to access unlicensedspectrum, generally, any operator or device may gain access. Sharedspectrum may fall between licensed and unlicensed spectrum, whereintechnical rules or limitations may be required to access the spectrum,but the spectrum may still be shared by multiple operators and/ormultiple RATs. For example, the holder of a license for a portion oflicensed spectrum may provide licensed shared access (LSA) to share thatspectrum with other parties, e.g., with suitable licensee-determinedconditions to gain access.

The air interface in the radio access network 200 may utilize one ormore duplexing algorithms. Duplex refers to a point-to-pointcommunication link where both endpoints can communicate with one anotherin both directions. Full duplex means both endpoints can simultaneouslycommunicate with one another. Half duplex means only one endpoint cansend information to the other at a time. In a wireless link, a fullduplex channel generally relies on physical isolation of a transmitterand receiver, and suitable interference cancellation technologies. Fullduplex emulation is frequently implemented for wireless links byutilizing frequency division duplex (FDD) or time division duplex (TDD).In FDD, transmissions in different directions operate at differentcarrier frequencies. In TDD, transmissions in different directions on agiven channel are separated from one another using time divisionmultiplexing. That is, at some times the channel is dedicated fortransmissions in one direction, while at other times the channel isdedicated for transmissions in the other direction, where the directionmay change very rapidly, e.g., several times per slot.

In order for transmissions over the radio access network 200 to obtain alow block error rate (BLER) while still achieving very high data rates,channel coding may be used. That is, wireless communication maygenerally utilize a suitable error correcting block code. In a typicalblock code, an information message or sequence is split up into codeblocks (CBs), and an encoder (e.g., a CODEC) at the transmitting devicethen mathematically adds redundancy to the information message.Exploitation of this redundancy in the encoded information message canimprove the reliability of the message, enabling correction for any biterrors that may occur due to the noise.

By way of example, user data may be coded using quasi-cyclic low-densityparity check (LDPC) with two different base graphs: one base graph isused for large code blocks and/or high code rates, while the other basegraph is used otherwise. Control information and the physical broadcastchannel (PBCH) are coded using polar coding, based on nested sequences.For these channels, puncturing, shortening, and repetition are used forrate matching.

However, those of ordinary skill in the art will understand that aspectsof the present disclosure may be implemented utilizing any suitablechannel code. Various implementations of scheduling entities (e.g., basestation 108) and scheduled entities (e.g., UE 106) may include suitablehardware and capabilities (e.g., an encoder, a decoder, and/or a CODEC)to utilize one or more of these channel codes for wirelesscommunication.

The air interface in the radio access network 200 may utilize one ormore multiplexing and multiple access algorithms to enable simultaneouscommunication of the various devices. An examples of multiple access mayinclude multiple access for UL transmissions from UEs 222 and 224 tobase station 210, and for multiplexing for DL transmissions from basestation 210 to one or more UEs 222 and 224, utilizing orthogonalfrequency division multiplexing (OFDM) with a cyclic prefix (CP). Inaddition, for UL transmissions, discrete Fourier transform-spread-OFDM(DFT-s-OFDM) with a CP (also referred to as single-carrier FDMA(SC-FDMA)) may be used. However, within the scope of the presentdisclosure, multiplexing and multiple access are not limited to theabove schemes, and may be provided utilizing time division multipleaccess (TDMA), code division multiple access (CDMA), frequency divisionmultiple access (FDMA), sparse code multiple access (SCMA), resourcespread multiple access (RSMA), or other suitable multiple accessschemes. Further, multiplexing DL transmissions from the base station210 to UEs 222 and 224 may be provided utilizing time divisionmultiplexing (TDM), code division multiplexing (CDM), frequency divisionmultiplexing (FDM), orthogonal frequency division multiplexing (OFDM),sparse code multiplexing (SCM), or other suitable multiplexing schemes.

FIG. 3 illustrates an example block diagram of a base station and aplurality of UEs 303 a and 303 b. In this example, the base station 301may be equipped with N_(t) antennas 324 a through 324 ap. A first UE 303a may be equipped with one or more N_(ut,m) antennas 352 ma through 352mu, and a second UE 303 b may be equipped with one or more N_(ut,x)antennas 352 xa through 352 xu. In accordance with the explanationprovided above, the base station 301 may be a transmitting entity forthe DL and a receiving entity for the UL. Each UE 303 a and 303 b may bea transmitting entity for the UL and a receiving entity for the DL. Asused herein, a “transmitting entity” is an independently operatedapparatus or device capable of transmitting data using a wirelesschannel, and a “receiving entity” is an independently operated apparatusor device capable of receiving data using a wireless channel. In thefollowing description, the subscript “dn” denotes the DL, the subscript“up” denotes the UL, N_(up) UEs are selected for simultaneoustransmission on the UL, N_(dn) UEs are selected for simultaneoustransmission on the DL, N_(up) may or may not be equal to N_(dn), andN_(up) and N_(dn) may be static values or can change for each schedulinginterval. The beam-steering or some other spatial processing techniquemay be used at the base station 301 and/or UEs 303 a and 303 b.

On the UL, at each UE 303 a and 303 b selected for uplink transmission,a transmit (TX) data processor 388 receives traffic data from a datasource 386 and control data from a controller 380. The controller 380may be coupled with a memory 382. TX data processor 388 processes (e.g.,encodes, interleaves, and modulates) the traffic data for the UE basedon the coding and modulation schemes associated with the rate selectedfor the UE and provides a data symbol stream. A TX spatial processor 390performs spatial processing on the data symbol stream and providesN_(ut,m) transmit symbol streams for the N_(ut,m) antennas. Eachtransmitter unit (TMTR) 354 receives and processes (e.g., converts toanalog, amplifies, filters, and frequency upconverts) a respectivetransmit symbol stream to generate an uplink signal. N_(ut,m)transmitter units 354 provide N_(ut,m) uplink signals for transmissionfrom N_(ut,m) antennas 352 to the base station 301.

Up to N_(up) UEs may be scheduled for simultaneous transmission on theuplink. Each of these UEs may perform spatial processing on its datasymbol stream and transmits its set of transmit symbol streams on theuplink to the base station.

At the base station 301, N_(ap) antennas 324 a through 324 ap receivethe uplink signals from all N_(up) UEs transmitting on the uplink. Eachantenna 324 provides a received signal to a respective receiver unit(RCVR) 322. Each receiver unit 322 performs processing complementary tothat performed by transmitter unit 354 and provides a received symbolstream. An RX spatial processor 340 performs receiver spatial processingon the N_(ap) received symbol streams from N_(ap) receiver units 322 andprovides N_(up) recovered uplink data symbol streams. The receiverspatial processing is performed in accordance with the channelcorrelation matrix inversion (CCMI), minimum mean square error (MMSE),soft interference cancellation (SIC), or some other technique. Eachrecovered uplink data symbol stream is an estimate of a data symbolstream transmitted by a respective UE. An RX data processor 342processes (e.g., demodulates, deinterleaves, and decodes) each recovereduplink data symbol stream in accordance with the rate used for thatstream to obtain decoded data. The decoded data for each UE 303 a and303 b may be provided to a data sink 344 for storage and/or a controller330 for further processing. The controller 330 may be coupled with amemory 332.

On the downlink, at the base station 301, a TX data processor 310receives traffic data from a data source 308 for N_(dn) UEs scheduledfor downlink transmission, control data from a controller 330, andpossibly other data from a scheduler 334. The various types of data maybe sent on different transport channels. TX data processor 310 processes(e.g., encodes, interleaves, and modulates) the traffic data for each UEbased on the rate selected for that UE. The TX data processor 310provides N_(dn) downlink data symbol streams for the N_(dn) UEs. A TXspatial processor 320 performs spatial processing (such as a precodingor beamforming, as described in the present disclosure) on the N_(dn)downlink data symbol streams, and provides N_(ap) transmit symbolstreams for the N_(ap) antennas. Each transmitter unit 322 receives andprocesses a respective transmit symbol stream to generate a downlinksignal. N_(ap) transmitter units 322 providing N_(ap) downlink signalsfor transmission from N_(ap) antennas 324 to the UEs. The decoded datafor each UE may be provided to a data sink 372 for storage and/or acontroller 380 for further processing.

At each UE, one or more N_(ut,m) antennas 352 receive the N_(ap)downlink signals from the base station 301. Each receiver unit 354processes a received signal from an associated antenna 352 and providesa received symbol stream. An RX spatial processor 360 performs receiverspatial processing on N_(ut,m) received symbol streams from N_(ut,m)receiver units 354 and provides a recovered downlink data symbol streamfor the UE. The receiver spatial processing is performed in accordancewith the CCMI, MMSE or some other technique. An RX data processor 370processes (e.g., demodulates, deinterleaves and decodes) the recovereddownlink data symbol stream to obtain decoded data for the UE.

At each UE 303, a channel estimator 378 estimates the downlink channelresponse and provides downlink channel estimates, which may includechannel gain estimates, signal-to-noise ratio (SNR) estimates, noisevariance and so on. Similarly, at the base station 301, a channelestimator 328 estimates the uplink channel response and provides uplinkchannel estimates. The controller 380 for each UE typically derives thespatial filter matrix for the UE based on the downlink channel responsematrix H_(dn,m) for that UE. The controller 330 derives the spatialfilter matrix for the base station based on the effective uplink channelresponse matrix H_(up,eff). The controller 380 for each UE may sendfeedback information (e.g., the downlink and/or uplink eigenvectors,eigenvalues, SNR estimates, and so on) to the base station. Thecontrollers 330 and 380 also control the operation of various processingunits at base station 301 and UE 303, respectively.

While portions of the present disclosure describe the UEs 303 capable ofcommunicating using multiple input multiple output (MIMO) techniques,for certain aspects the UEs 303 may also include some UEs that do notsupport MIMO. Thus, for such aspects, the base station 301 may beconfigured to communicate with both MIMO and non-MIMO UEs. This approachmay conveniently allow older versions of UEs, known as “legacy” UEs, toremain deployed in an enterprise, extending their useful lifetime whileallowing newer MIMO UEs to be introduced as deemed appropriate.

A frame structure may be used for data transmission between wirelessstations such as a transmitter station and a receiver station. In oneaspect, a frame structure in a Media Access Control (MAC) layer and aphysical (PHY) layer is utilized, wherein in a transmitter station, aMAC layer receives a MAC Service Data Unit (MSDU) and attaches a MACheader thereto, in order to construct a MAC Protocol Data Unit (MPDU).The MAC header includes information such as a source address (SA) and adestination address (DA). The MPDU is a part of a PHY Service Data Unit(PSDU) and is transferred to a PHY layer in the transmitter to attach aPHY header (i.e., PHY preamble) thereto to construct a PHY Protocol DataUnit (PPDU). The PHY header includes parameters for determining atransmission scheme including a coding/modulation scheme. The PHY layerincludes transmission hardware for transmitting data bits over awireless link. Before transmission as a frame from the transmitterstation to the receiver station, a preamble is attached to the PPDU,wherein the preamble can include channel estimation and synchronizationinformation.

FIG. 4 illustrates a schematic of an example of an OFDM waveform framestructure. It should be understood by those of ordinary skill in the artthat the various aspects of the present disclosure may be applied to aDFT-s-OFDMA waveform in substantially the same way as described hereinbelow. That is, while some examples of the present disclosure may focuson an OFDM link for clarity, it should be understood that the sameprinciples may be applied as well to DFT-s-OFDMA waveforms.

Within the present disclosure, a frame may refer to a duration of 10 msfor wireless transmissions, with each frame consisting of 10 subframesof 1 ms each. On a given carrier, there may be one set of frames in theUL, and another set of frames in the DL. Referring now to FIG. 4, anexpanded view of an example DL subframe 402 is illustrated, showing anOFDM resource grid 404. However, as those skilled in the art willreadily appreciate, the PHY transmission structure for any particularapplication may vary from the example described here, depending on anynumber of factors. Here, time is in the horizontal direction with unitsof OFDM symbols; and frequency is in the vertical direction with unitsof subcarriers or tones.

The resource grid 404 is divided into multiple resource elements (REs)406. An RE, which is 1 subcarrier×1 symbol, is the smallest discretepart of the time-frequency grid, and contains a single complex valuerepresenting data from a physical channel or signal. Depending on themodulation utilized in a particular implementation, each RE mayrepresent one or more bits of information or parity bits. In someexamples, a block of REs may be referred to as a physical resource block(PRB) or more simply a resource block (RB) 408, which contains anysuitable number of consecutive subcarriers in the frequency domain. Inone example, an RB may include 12 subcarriers, or another numberindependent of the numerology used. In some examples, depending on thenumerology, an RB may include any suitable number of consecutive OFDMsymbols in the time domain.

A UE generally utilizes only a subset of the resource grid 404. An RBmay be the smallest unit of resources that can be allocated to a UE.Thus, the more RBs scheduled for a UE, and the higher the modulationscheme chosen for the air interface, the higher the data rate for theUE. In this illustration, the RB 408 is shown as occupying less than theentire bandwidth of the subframe 402, with some subcarriers illustratedabove and below the RB 408.

Each 1 millisecond (ms) subframe 402 may consist of one or multipleadjacent slots. In the example shown in FIG. 4, one subframe 402includes four slots 410, as an illustrative example. In some examples, aslot may be defined according to a specified number of OFDM symbols witha given cyclic prefix (CP) length. For example, a slot may include 7 or14 OFDM symbols with a nominal CP. Additional examples may includemini-slots having a shorter duration (e.g., one or two OFDM symbols).These mini-slots may in some cases be transmitted occupying resourcesscheduled for ongoing slot transmissions for the same or for differentUEs.

An expanded view of one of the slots 410 illustrates the slot 410including a control region 412 and a data region 414. In general, thecontrol region 412 may carry control channels (e.g., a physical downlinkcontrol channel), and the data region 414 may carry data channels (e.g.,physical downlink shared channel or physical uplink shared channel). Ofcourse, a slot may contain all DL, all UL, or at least one DL portionand at least one UL portion. The simple structure illustrated in FIG. 4is merely example in nature, and different slot structures may beutilized, and may include one or more of each of the control region(s)and data region(s).

Although not illustrated in FIG. 4, the various REs 406 within a RB 408may be scheduled to carry one or more physical channels, includingcontrol channels, shared channels, data channels, etc. For example, oneor more control channels may be used for scheduling and controllingranging operations between UEs. Other REs 406 within the RB 408 may alsocarry pilots or reference signals, including but not limited to ademodulation reference signal (DMRS) a control reference signal (CRS),or a sounding reference signal (SRS). These pilots or reference signalsmay provide for a receiving device to perform channel estimation of thecorresponding channel, which may enable coherent demodulation/detectionof the control and/or data channels within the RB 408.

The channels or carriers described above and illustrated in FIGS. 1-4are not necessarily all the channels or carriers that may be utilizedbetween a scheduling entity 108 and scheduled entities 106, and those ofordinary skill in the art will recognize that other channels or carriersmay be utilized in addition to those illustrated, such as other traffic,control, and feedback channels.

These physical channels described above are generally multiplexed andmapped to transport channels for handling at the medium access control(MAC) layer. Transport channels carry blocks of information calledtransport blocks (TB). The transport block size (TBS), which maycorrespond to a number of bits of information, may be a controlledparameter, based on the modulation and coding scheme (MCS) and thenumber of RBs in a given transmission.

Since transmissions over a wireless channel are often susceptible tointerference which may result in errors to the transmissions, techniquesto reduce such errors and/or help recover affected data/information inthe transmissions are desirable.

As mentioned previously, channel coding may help improve reliablecommunication and error detection. Various aspects provide methods andapparatus for self-decodability of HARQ transmissions that are encodedusing a low-density parity-check (LDPC) code. A plurality of bits N areencoded using an LDPC code that employs a quasi-cyclic liftingstructure, which is a sparse bipartite graph (also referred to as a basegraph). The encoded bits may result into a first set of bits encodedwith a core (systematic) part of the base graph which are referred to ascore or systematic bits, and a second set of bits encoded with anon-core (parity) part of the base graph which are referred to asnon-core or parity bits. In some implementations, the core (systematic)part of the base graph may be more densely populated than the non-core(parity) part of the graph. After puncturing of the encoded bits, theresulting encoded bits are transmitted from a circular buffer accordingto a first redundancy version order. However, if a retransmission isrequired, then the first set of bits (i.e., core or systematic bits) arereordered (e.g., using an interleaver). The second set of bits (non-coreor parity bits) are not reordered. After reordering of the first set ofbits, some of the reordered resulting encoded bits are transmitted froma circular buffer according to a second redundancy version. By modifyingor reordering the core or systematic bits and transmitting some of them(e.g., a subset of all reordered bits), a probability that the secondredundancy version will be self-decodable by a receiver is improved. Ifadditional retransmissions are needed, the reordered first set of bits(core or systematic bits) may be used and some of them transmittedaccording to a different redundancy version.

Transmissions over a channel are often susceptible to interference orfading which may result in errors to the transmissions. Varioustechniques have been employed to reduce such errors and/or help recoveraffected data/information in the transmissions. For instance, turbocodes have been used in many modern cellular systems for forward errorcorrection (FEC). In some technologies, low-density parity-check (LDPC)codes for forward error correction are used. A low-density parity-check(LDPC) code (also known as a Galleger code) is a linear error correctingcode constructed using a sparse bipartite graph. LDPC codes may allowfor high throughput. Additionally, channel coding may also need tosupport incremental-redundancy hybrid automatic repeat request (HARQ),and a wide range of block lengths and coding rates, with stringentperformance guarantees and minimal overhead complexity. HARQ are used toensure high transmission reliability.

Hybrid automatic repeat request (hybrid ARQ or HARQ) is a combination ofhigh-rate forward error-correcting coding and ARQ error-control. Instandard ARQ, redundant bits are added to data to be transmitted usingan error-detecting (ED) code such as a cyclic redundancy check (CRC).Receivers detecting a corrupted message can request a new message fromthe sender. In HARQ, the original data is encoded with a forward errorcorrection (FEC) code, and the parity bits are either immediately sentalong with the message or only transmitted upon request when a receiverdetects an erroneous message. The ED code may be omitted when a code isused that can perform both forward error correction (FEC) in addition toerror detection, such as a Reed-Solomon code. The FEC code is chosen tocorrect an expected subset of all errors that may occur, while the ARQmethod is used as a fall-back to correct errors that are uncorrectableusing only the redundancy sent in the initial transmission. As a result,HARQ may perform better than ARQ in poor signal conditions, but may comeat the expense of significantly lower throughput in good signalconditions. There is sometimes a signal quality crossover point belowwhich simple HARQ is better, and above which basic ARQ is better.

FIG. 5 is an example matrix illustrating a 5G NR LDPC code structureusing a sparse bipartite graph 500 (e.g., base graph) comprising asystematic part 502 and a parity part 504. The NR LDPC code employsquasi-cyclic lifting structure (e.g., a base graph) which enablesparallel decoding. The core or systematic part 502 (also referred to asnodes with a degree greater than 1) is denser than the non-core orparity part 504. The core part 502 may be identified based on thepresence of more than one non-zero value per column while the non-corepart or parity part includes some columns with only one non-zero value.The non-core or parity part 504 (also referred to as nodes with a degree1 extension) facilitates flexible HARQ transmission. In one example, thegraph 500 may have 42 rows and 52 columns, with 10 columns being for thecore or systematic part and 38 columns being for the non-core or paritypart.

Although FIG. 5 illustrates a matrix which may be used to decode amessage received via a channel, the matrix sufficiently defines thecorresponding LDPC code such that an encoding or generator matrix may bedetermined for use during an encoding operation. The matrix may bepredefined such that both a transmitter and a receiver encode and decodesignals in accordance with a common LDPC code.

FIG. 6 is a block diagram illustrating an example of a HARQ transmissionprocess using a low-density parity-check (LDPC) code. Information andfiller bits 602 are encoded 604 based on the sparse bipartite graph 500(e.g., base graph). Puncturing is then applied to the encoded bits toremove some parity bits 606. The coded bits are then placed into acircular buffer 608. Bits are then selected according to a redundancyversion order (RV) 610 and sent to a constellation mapper 612 inpreparation for transmission.

FIG. 7 illustrates an example of a circular buffer 704 and redundancyversion order 702 for a HARQ transmission. In this example, four (4)redundancy version (RV) orders 702 are defined, with a maximum of 4transmissions. Each redundancy version order may start at a differentcolumn of the sparse bipartite graph 500. A RV order defines thestarting position (e.g., starting column) of each transmission. Forexample, RV0 starts at column 0, or at the first bit of the encoded datacomputed in accordance with the LDPC code of FIG. 5. RV1 starts atcolumn 13 (or the 14th bit), RV 2 starts at the 25th column (or the 26thbit), and RV 3 starts at the 43rd column (or the 44th bit).

The circular buffer 704 contains coded bits (excluding shortened bits)corresponding to a minimum rate Rmin. A first transmission uses a firstredundancy version order RV0 while retransmissions may start at adifferent redundancy version order RV1, RV2, or RV3. Typically, usingthe RV order of RV0, RV2, RV3, RV1 gives good performance. The actuallength of the retransmission may cause the bits to be transmitted toextend past an end of the encoded data and continue from the beginningof the encoded bits. For example, if RV3 is of sufficient length, itwill extend from column 43 to the end and continue from the beginninguntil the number of bits corresponding to the length of RV3 is reached.

In some cases, a retransmitted sequence may not supportself-decodability. That is, there may be cases where only parity bits(non-core part 504) are transmitted. In at least some cases, if theretransmitted sequence does not include bits in the systematic or corepart 502, it cannot be self-decoded. For example, RV1 starts after thesystematic bits and may not be long enough to circle back around to thebeginning of the buffer to the start of the systematic bits. Insituations where self-decodability for each RV is desired, RVS basedonly on the original ordering of the encoded bits may be insufficient.

FIG. 8 is a block diagram illustrating a HARQ transmission process 800to facilitate self-decodability. This process 800 is similar to theprocess 600 (FIG. 6), but a modified circular buffer 808 is used.According to one embodiment, the modified circular buffer 808 is“modified” in that an ordering of bits within the circular buffer 808 ismodified or changes from an original encoded order of bits. In thismodified circular buffer, there may be no change for the firsttransmission, such as when bits are transmitted according to RV0discussed previously.

If a retransmission is required, then the original order of encoded bitsmay be modified. For example, the core or systematic bits in thecircular buffer may be reordered and at least some of the t bits fromthe core or systematic part of the base graph are included in theretransmission. For instance, the bits in the core or systematic partmay be permutated (e.g., pseudo-randomly or pseudo-cyclicallyreordered), and the modified circular buffer 408 is filled first withpermutated core or systematic bits and then with non-core or parity bitsin their original order. Such permutation may be random or in arow-column pattern. According to one example, for a retransmission t, afraction α_(t) of the bits are selected from the core or systematicpart, where a total of N_(t) bits are to be transmitted and t≥0. Thenumber of retransmitted core/systematic bits is K_(t)=[α_(t)N_(c)],0<α_(t)<1, where N_(c) is the total number of bits in the core orsystematic part (e.g., core or systematic bits). Then, the total numberof bits in the non-core or parity part (e.g., non-core or parity bits)with RV order are N_(t) ^(p)=N_(t)−K_(t).

FIG. 9 illustrates an example of how encoded bits, such as those withina circular buffer, may be reordered for or during a retransmission. Inthe illustrated embodiment, only core bits 902 are passed through aninterleaver 904 to reorder them. The interleaver 904 may be a row-columninterleaver or other type of interleaver that results in the reorderingof the core or systematic bits 902. The interleaved core bits 902′ areused to fill part of the circular buffer while the rest of the circularbuffer is filled by the non-core bits 904 without change in their order.The reordering may be done within the circular buffer, such as byretrieving the core bits, passing them through an interleaver, andstoring them again in the circular buffer. The reordering may also bedone by pulling out the bits in a different order than they are storedwithin the buffer. For example, an interleaver may be used for selectingbits from within encoded bits or circular buffer during a transmissionprocess. The illustrated reordering may represent the logical effect ofthe resulting order of stored or transmitted bits.

FIG. 10 illustrates HARQ transmissions using low-density parity-check(LDPC) coding and reordering of a circular buffer duringretransmissions. During a first transmission, a circular buffer 1000 isfilled with bits encoded using an LDPC code that employs a quasi-cycliclifting structure (e.g., a sparse bipartite graph or a base graph).These coded bits may include a first set of bits 1002 encoded with acore (systematic) part of the base graph which are referred to as coreor systematic bits. The coded bits may also include a second set of bits1004 encoded with a non-core (parity) part of the base graph which arereferred to as non-core or parity bits. A plurality of encoded bits N₀from the circular buffer 1000 are transmitted 1008 according to a bitselection defined by a first redundancy version order (RV0). As shown,N₀ starts at a beginning of the encoded bits and extends through thecore bits into non-core bits.

If a retransmission of this data is required, then the core bits 1002are reordered (either logically or within the buffer) to obtainreordered bits 1002′. A retransmission circular buffer 1006 may befilled with the reordered core bits 1002′ and the non-core (parity) bits1004. A first plurality of core bits K₁, and a second plurality ofnon-core bits N₁ ^(p) are then transmitted 1010 from the circular buffer1006 according to a bit selection defined by a second redundancy versionorder (e.g., RV2).

If yet another retransmission of this data is required, then the orderof the reordered bits 1002′ may be maintained, but a different portionof the reordered bits are selected for retransmission. A secondplurality of core bits K₂, and a third plurality of non-core bits N₂^(p) are then transmitted from the circular buffer 1006 according to abit selection defined by a third redundancy version order (e.g., RV3).An additional retransmission may select a third plurality of core bitsand a fourth plurality of non-core bits may be transmitted.

The illustrated reordering may be performed by moving or replacingordered bits with reordered bits or may be performed during read out ofbits for transmission. For example, the encoded bits within the circularbuffer may stay in their original order but the bits may be read out ina reordered fashion during retransmission. This may help limit memoryrequirements, limit complexity of the circular buffer and associatedcircuitry, or limit time needed to generate the reordered bits. Asillustrated by K₁ and N₁ being non-consecutive bits, the bits may beread out in a different order than actually stored.

In one implementation, the reordering may be performed to guarantee thatsome fraction of the core bits will be transmitted in eachretransmission. The fraction of core bits picked in each retransmissionmay depend on the transmission rate and block length. A good choice forthe fraction α_(t) would result in a good tradeoff between HARQ gain andself-decodability. In at least one implementation the manner forreordering encoded bits, the starting points K₁, N₁, K₂, N₂, and thelike may be predetermined such that a receiver can correctly identifywhich information or parity bits are at which locations in thetransmission.

FIG. 11 is a block diagram illustrating an example of a bit encoding andtransmission circuit. A bit stream 1102 is received by an encodercircuit 1104 where an encoder 1104 for encoding data using a low-densityparity check code encoder 1114 to obtain encoded data, where the encodeddata includes core data and non-core data. For instance, the low-densityparity-check (LDPC) code encoder 1114 may apply a base graph 1116 toobtain encoded bits. The base graph 1116 may include a quasi-cycliclifting structure, which may be a sparse bipartite graph. The encodedbits may include a first set of bits encoded with a core (systematic)part of the base graph which are referred to as core or systematic bits,and a second set of bits encoded with a non-core (parity) part of thebase graph which are referred to as non-core or parity bits. The encodedbits may be sent to a systematic bit puncturing circuit 1106 whichremoves some of non-core (parity) bits. A transmitter circuit 1109 maybe configured for transmitting a plurality of redundancy versions of theencoded data, wherein all redundancy versions of encoded data includecore data, and each of the transmitted redundancy versions of theencoded data includes at least a different subset of the core data.

In one example, the encoded bits are then received at the modifiedbuffer circuit 1108 for storing the encoded data for transmission. On afirst transmission, the encoded bits may be placed on a circulartransmit buffer 1118 from where a redundancy version ordering circuit1110 extracts them for transmission, according to a first redundancyversion order, through a constellation mapper 1112.

If the encoded bits are to be retransmitted, then an interleaver 1120modifies the order of the first set of bits and places them in acircular retransmit buffer 1122 for transmission according to adifferent redundancy version order. Alternatively, the bits may be leftin their original encoded order and read out/transmitted according to areordering. Note that the circular transmit buffer 1118 may be reused asthe circular retransmit buffer 1122. By reordering the core orsystematic bits for retransmission, it may be guaranteed that the secondor other subsequent redundancy version will transmit some of the core orsystematic bits, which greatly increases the probably forself-decodability by a receiver. If additional retransmissions areneeded, the reordered first set of bits (core or systematic bits) may beused and transmitted according to a different redundancy version orders.

In some implementations, the core data is reordered prior to obtainingat least one of the different subsets of core data.

According to one example, a transmission of a first redundancy versionof the encoded data may include all of the core data, while atransmission of a second redundancy version of the encoded data mayinclude only a subset of the core data.

In some instances, transmitting the plurality of redundancy versions ofthe encoded data may include: (a) transmitting a first redundancyversion of the encoded data, wherein the first redundancy version of theencoded data includes at least a first subset of the core data; (b)transmitting a second redundancy version of the encoded data, whereinthe second redundancy version of the encoded data includes at least asecond subset of the core data different from the first subset of coredata, and where the core data is reordered prior to obtaining the secondsubset of core data; and/or (c) transmitting a third redundancy versionof the encoded data, wherein the third redundancy version of the encodeddata includes at least a third subset of the core data different fromthe first and second subsets of core data, and the same reordered coredata is used to obtain the second and third subsets of core data.

FIG. 12 is a block diagram of an example of a communication apparatusconfigured to perform hybrid automatic repeat request (HARQ)transmissions using low-density parity-check (LDPC) coding whilereordering a buffer for retransmissions. The apparatus 1202 may includea processing circuit 1204 coupled to a machine-readable medium 1206. Themachine-readable medium may store one or more instructions which whenexecuted by the processing circuit, causes the processing circuit to:(a) encode data using a low-density parity check code to obtain encodeddata, where the encoded data includes core data and non-core data; (b)store the encoded data in a buffer for transmission; and/or (c) transmita plurality of redundancy versions of the encoded data, wherein allredundancy versions of encoded data include core data, and each of thetransmitted redundancy versions of the encoded data includes at least adifferent subset of the core data. The instructions may includereordering the core data prior to obtaining at least one of thedifferent subsets of core data.

While in some implementations the LDPC coding may be used as part ofHARQ transmission, it is contemplated that the modified LDPC coding tobe applicable to other types of transmissions as well.

FIG. 13 illustrates an example of a method for HARQ transmissions usinglow-density parity-check (LDPC) coding and reordering of a buffer duringretransmissions. The method may be implemented, for example, in thedevice/apparatus illustrated in FIGS. 11 and 12. Data may be encodedusing a low-density parity check code to obtain encoded data, where theencoded data includes core data and non-core data 1302. The low-densityparity check code may use a quasi-cyclic lifting structure. Forinstance, the quasi-cyclic lifting structure may be a sparse bipartitegraph having a core part that is more densely populated than a non-corepart. The non-core data may include parity data for forward errorcorrection.

The encoded data may then be stored in a buffer for transmission 1304.In one example, the buffer may be a circular buffer.

A plurality of redundancy versions of the encoded data may be selectedfrom a set of redundancy versions, where the set of redundancy versionsand their transmission order is preconfigured, and wherein each of theset of redundancy versions includes sufficient core data to permitself-decodability 1306. The plurality of redundancy versions of theencoded data is then transmitted, wherein all redundancy versions ofencoded data include core data, and each of the transmitted redundancyversions of the encoded data includes at least a different subset of thecore data 1308. The core data may be reordered prior to obtaining atleast one of the different subsets of core data. Alternatively, the coredata may be retrieved according to a new order to obtain the at leastone of the different subsets of core data.

In some aspects, a transmission of a first redundancy version of theencoded data includes all of the core data, while a transmission of asecond redundancy version of the encoded data includes fewer than all ofthe core data.

In one example, each of the transmitted redundancy versions of theencoded data includes sufficient core data to permit self-decodabilityof the transmission at a receiver.

In a second example, each of the set of redundancy versions may have afirst starting point for the core data and a second starting point forthe non-core data, which are known to the intended receiver.

According to another example, transmitting a plurality of redundancyversions of the encoded data may include: (a) transmitting a firstredundancy version of the encoded data, wherein the first redundancyversion of the encoded data includes at least a first subset of the coredata; (b) transmitting a second redundancy version of the encoded data,wherein the second redundancy version of the encoded data includes atleast a second subset of the core data different from the first subsetof core data, and where the core data is reordered prior to obtainingthe second subset of core data; and/or (c) transmitting a thirdredundancy version of the encoded data, wherein the third redundancyversion of the encoded data includes at least a third subset of the coredata different from the first and second subsets of core data, and thesame reordered core data is used to obtain the second and third subsetsof core data. In one example, the first subset of the core data mayinclude all the core data. In another example, the second subset of thecore data may include fewer than all the core data. In yet anotherexample, the second redundancy version of the encoded data includes morenon-core data than the first redundancy version of the encoded data. Thesecond redundancy version of the encoded data may be transmitted uponreceipt of an indicator to retransmit the encoded data. In someimplementations, the first redundancy version of the encoded data mayhave a higher transmission rate for the data than the second redundancyversion of the encoded data.

FIG. 14 is a block diagram illustrating an example of a receiver anddata decoding circuit. A receiver circuit 1402 may be configured toreceive a plurality of redundancy versions of encoded data, where theencoded data includes core data and non-core data, wherein each of thereceived redundancy versions of the encoded data includes at least adifferent subset of the core data. A data aggregation circuit 1404 maybe coupled to the receiver circuit and configured to obtain the encodeddata from one or more of the plurality of redundancy versions of encodeddata. For instance, the encoded data may be obtained by combininglikelihood ratios for the received plurality of redundancy versions ofthe encoded data. In one example, a first redundancy version of theencoded data includes all of the core data, while a second redundancyversion of the encoded data includes less than all the core data.

A decoding circuit 1406 may serve to decode the encoded data using alow-density parity check code to obtain decoded data.

In one example implementation, the receiver circuit may be furtherconfigured to: (a) receive a first redundancy version of the encodeddata, wherein the first redundancy version of the encoded data includesat least a first subset of the core data; (b) receive a secondredundancy version of the encoded data, wherein the second redundancyversion of the encoded data includes at least a second subset of thecore data different from the first subset of core data, and where thesecond subset of core data is based on a reordered version of the coredata relative to the first subset of core data, and/or (c) receive athird redundancy version of the encoded data, wherein the thirdredundancy version of the encoded data includes at least a third subsetof the core data different from the first and second subsets of coredata, and the second subset and third subset of core data is based onthe same reordered core data.

FIG. 15 is a block diagram of an example of a communication apparatusconfigured to perform hybrid automatic repeat request (HARQ) receptionusing a modified low-density parity-check (LDPC) coding. The apparatus1502 may include a processing circuit 1504 coupled to a machine-readablemedium 1506. The machine-readable medium may include one or moreinstructions which when executed by the processing circuit, causes theprocessing circuit to: (a) receive a plurality of redundancy versions ofencoded data, where the encoded data includes core data and non-coredata, wherein each of the received redundancy versions of the encodeddata includes at least a different subset of the core data; (b) obtainthe encoded data from one or more of the plurality of redundancyversions of encoded data; and/or (c) decode the encoded data using alow-density parity check code to obtain decoded data.

In one example, the machine-readable medium may further include one ormore instructions which when executed by the processing circuit, causesthe processing circuit to: (a) receive a first redundancy version of theencoded data, wherein the first redundancy version of the encoded dataincludes at least a first subset of the core data; (b) receive a secondredundancy version of the encoded data, wherein the second redundancyversion of the encoded data includes at least a second subset of thecore data different from the first subset of core data, and where thesecond subset of core data is based on a reordered version of the coredata relative to the first subset of core data; and/or (c) receive athird redundancy version of the encoded data, wherein the thirdredundancy version of the encoded data includes at least a third subsetof the core data different from the first and second subsets of coredata, and the second subset and third subset of core data is based onthe same reordered core data.

In one example implementation, the machine-readable medium may furtherinclude one or more instructions which when executed by the processingcircuit, causes the processing circuit to: (a) receive a firstredundancy version of the encoded data, wherein the first redundancyversion of the encoded data includes at least a first subset of the coredata; (b) receive a second redundancy version of the encoded data,wherein the second redundancy version of the encoded data includes atleast a second subset of the core data different from the first subsetof core data, and where the second subset of core data is based on areordered version of the core data relative to the first subset of coredata, and/or (c) receive a third redundancy version of the encoded data,wherein the third redundancy version of the encoded data includes atleast a third subset of the core data different from the first andsecond subsets of core data, and the second subset and third subset ofcore data is based on the same reordered core data.

FIG. 16 is a block diagram illustrating an example of a method forreceiving hybrid automatic repeat request (HARQ) transmissions usinglow-density parity-check (LDPC) coding with reordered retransmissions.The method may be implemented, for example, in a receiverdevice/apparatus illustrated in FIGS. 14 and/or 15.

A plurality of redundancy versions of encoded data may be received(e.g., over the air) at the apparatus, where the encoded data includescore data and non-core data, wherein each of the received redundancyversions of the encoded data includes at least a different subset of thecore data 1602. In one example, the encoded data may be obtained bycombining likelihood ratios for the received plurality of redundancyversions of the encoded data. The non-core data may include parity datafor forward error correction.

A plurality of redundancy versions may be selected from a set ofredundancy versions, where the set of redundancy versions and theirtransmission order is pre-arranged with a transmitter 1604. In oneexample, each of the received redundancy versions of the encoded dataincludes sufficient core data to permit self-decodability of the encodeddata.

The encoded data may be obtained from one or more of the plurality ofredundancy versions of encoded data 1606. In one example, the encodeddata is obtained by combining likelihood ratios for the receivedplurality of redundancy versions of the encoded data. In oneimplementations, a first redundancy version of the encoded data includesall of the core data, while a second redundancy version of the encodeddata includes less than all the core data.

The encoded data may be decoded using a low-density parity check code toobtain decoded data 1608. The low-density parity check code may use aquasi-cyclic lifting structure. In one example, the quasi-cyclic liftingstructure may be a sparse bipartite graph having a core part that ismore densely populated than a non-core part.

Each of the set of redundancy versions may have a first starting pointfor the core data and a second starting point for the non-core data,which are provided to the receiver.

In one example implementation, receiving a plurality of redundancyversions of the encoded data may include: (a) receiving a firstredundancy version of the encoded data, wherein the first redundancyversion of the encoded data includes at least a first subset of the coredata; (b) receiving a second redundancy version of the encoded data,wherein the second redundancy version of the encoded data includes atleast a second subset of the core data different from the first subsetof core data, and where the second subset of core data is based on areordered version of the core data relative to the first subset of coredata, and/or (c) receiving a third redundancy version of the encodeddata, wherein the third redundancy version of the encoded data includesat least a third subset of the core data different from the first andsecond subsets of core data, and the second subset and third subset ofcore data is based on the same reordered core data. In one example, thefirst subset of the core data may include all the core data. In anotherexample, the second subset of the core data may include fewer than allthe core data. In some instances, the second redundancy version of theencoded data includes more non-core data than the first redundancyversion of the encoded data.

In one example, the receiver may send an indicator to retransmit theencoded data prior to receiving the second redundancy version of theencoded data.

In various implementations, a block length of the second redundancyversion of the encoded data may be different than first redundancyversion of the encoded data or it may be the same as first redundancyversion of the encoded data.

While certain example embodiments have been described and shown in theaccompanying drawings, it is to be understood that such embodiments aremerely illustrative of and not restrictive on the broad invention, andthat this invention not be limited to the specific constructions andarrangements shown and described, since various other modifications mayoccur to those ordinarily skilled in the art. The example embodimentsare provided to illustrate certain concepts of the disclosure. Those ofordinary skill in the art will appreciate that these are example innature, and other examples may fall within the scope of the disclosureand the appended claims.

As those of ordinary skill in the art will readily appreciate, variousaspects described throughout this disclosure may be extended to anysuitable telecommunication system, network architecture, andcommunication standard. By way of example, various aspects may beapplied to UMTS systems such as W-CDMA, TD-SCDMA, and TD-CDMA. Variousaspects may also be applied to systems employing Long Term Evolution(LTE) (in FDD, TDD, or both modes), LTE-Advanced (LTE-A) (in FDD, TDD,or both modes), LTE-Advanced Pro, 5G New Radio, CDMA 2000,Evolution-Data Optimized (EV-DO), Ultra Mobile Broadband (UMB), IEEE802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Ultra-Wideband (UWB),Bluetooth, and/or other suitable systems, including those described byyet-to-be defined wide area network standards. The actualtelecommunication standard, network architecture, and/or communicationstandard employed will depend on the specific application and theoverall design constraints imposed on the system.

Within the present disclosure, the word “example” is used to mean“serving as an example, instance, or illustration.” Any implementationor aspect described herein as “example” is not necessarily to beconstrued as preferred or advantageous over other aspects of thedisclosure. Likewise, the term “aspects” does not require that allaspects of the disclosure include the discussed feature, advantage, ormode of operation. The term “coupled” is used herein to refer to thedirect or indirect mechanical and/or electrical coupling between twoobjects. For example, if object A physically touches and/or electricallycommunicates with object B, and object B physically touches and/orelectrically communicates with object C, then objects A and C may stillbe considered coupled to one another—even if they do not directlyphysically touch and/or electrically communicate with each other. Forinstance, a first die may be coupled to a second die in a package eventhough the first die is never directly physically in contact with thesecond die. The terms “circuit” and “circuitry” are used broadly, andintended to include both hardware implementations of electrical devicesand conductors that, when connected and configured, enable theperformance of the functions described in the present disclosure,without limitation as to the type of electronic circuits, as well assoftware implementations of information and instructions that, whenexecuted by a processor, enable the performance of the functionsdescribed in the present disclosure.

One or more of the components, blocks, features, and/or functionsillustrated in above may be rearranged and/or combined into a singlecomponent, block, feature, or function or implemented in severalcomponents, blocks, features, and/or functions. Additional components,blocks, features, and/or functions may also be added without departingfrom novel features disclosed herein. The apparatus, devices, and/orcomponents illustrated above may be adapted (e.g., constructed,configured, employed, implemented, and/or programmed) to perform one ormore of the methods, blocks, features, and/or functions describedherein. The algorithms described herein may also be efficientlyimplemented in software and/or embedded in hardware.

It is to be understood that the specific order or hierarchy of blocks inthe methods disclosed is an illustration of example processes. It isunderstood that the specific order or hierarchy of blocks in the methodsmay be rearranged. The accompanying method claims present elements ofthe various blocks in a sample order, and are not meant to be limited tothe specific order or hierarchy presented unless specifically recitedtherein.

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. Thus, the claims are not intended to be limited to theaspects shown herein, but are to be accorded the full scope consistentwith the language of the claims, wherein reference to an element in thesingular is not intended to mean “one and only one” unless specificallyso stated, but rather “one or more.” Unless specifically statedotherwise, the term “some” refers to one or more. A phrase referring to“at least one of” a list of items refers to any combination of thoseitems, including single members. As an example, “at least one of: a, b,or c” is intended to cover: a; b; c; a and b; a and c; b and c; and a, band c. All structural and functional equivalents to the elements of thevarious aspects described throughout this disclosure that are known orlater come to be known to those of ordinary skill in the art areexpressly incorporated herein by reference and are intended to beencompassed by the claims. Moreover, nothing disclosed herein isintended to be dedicated to the public regardless of whether suchdisclosure is explicitly recited in the claims. No claim element is tobe construed under the provisions of 35 U.S.C. § 112(f), unless theelement is expressly recited using the phrase “means for” or, in thecase of a method claim, the element is recited using the phrase “stepfor.”

What is claimed is:
 1. A method for wireless communication at a transmitter, comprising: encoding data using a low-density parity check code to obtain encoded data, where the encoded data includes core data and non-core data; storing the encoded data in a buffer for transmission; and transmitting a plurality of redundancy versions of the encoded data, wherein all redundancy versions of encoded data include core data, and each of the transmitted redundancy versions of the encoded data includes at least a different subset of the core data.
 2. The method of claim 1, further comprising: reordering the core data prior to obtaining at least one of the different subsets of core data.
 3. The method of claim 1, wherein a transmission of a first redundancy version of the encoded data includes all of the core data, while a transmission of a second redundancy version of the encoded data includes fewer than all of the core data.
 4. The method of claim 1, wherein each of the transmitted redundancy versions of the encoded data includes sufficient core data to permit self-decodability of the transmission at a receiver.
 5. The method of claim 1, further comprising: selecting the plurality of redundancy versions from a set of redundancy versions, where the set of redundancy versions and their transmission order is preconfigured, and wherein each of the set of redundancy versions includes sufficient core data to permit self-decodability.
 6. The method of claim 5, wherein each of the set of redundancy versions has a first starting point for the core data and a second starting point for the non-core data, which are known to an intended receiver.
 7. The method of claim 1, wherein the non-core data includes parity data for forward error correction.
 8. The method of claim 1, wherein the low-density parity check code uses a quasi-cyclic lifting structure, where the quasi-cyclic lifting structure is a sparse bipartite graph having a core part that is more densely populated than a non-core part.
 9. The method of claim 1, wherein transmitting a plurality of redundancy versions of the encoded data includes: transmitting a first redundancy version of the encoded data, wherein the first redundancy version of the encoded data includes at least a first subset of the core data; and transmitting a second redundancy version of the encoded data, wherein the second redundancy version of the encoded data includes at least a second subset of the core data different from the first subset of the core data, and where the core data is reordered prior to obtaining the second subset of the core data.
 10. The method of claim 9, wherein the first subset of the core data includes all the core data, and the second subset of the core data includes fewer than all the core data.
 11. The method of claim 9, wherein the second redundancy version of the encoded data (a) includes more non-core data than the first redundancy version of the encoded data, and/or (b) is transmitted upon receipt of an indicator to retransmit the encoded data.
 12. The method of claim 9, wherein the first redundancy version of the encoded data has a higher transmission rate for the data than the second redundancy version of the encoded data.
 13. The method of claim 9, wherein transmitting the plurality of redundancy versions of the encoded data further includes: transmitting a third redundancy version of the encoded data, wherein the third redundancy version of the encoded data includes at least a third subset of the core data different from the first and second subsets of the core data, and the same reordered core data is used to obtain the second and third subsets of the core data.
 14. The method of claim 1, wherein the buffer is a circular buffer.
 15. An apparatus, comprising: an encoder for encoding data using a low-density parity check code to obtain encoded data, where the encoded data includes core data and non-core data; a buffer for storing the encoded data for transmission; a transmitter circuit configured for transmitting a plurality of redundancy versions of the encoded data, wherein all redundancy versions of encoded data include core data, and each of the transmitted redundancy versions of the encoded data includes at least a different subset of the core data.
 16. The apparatus of claim 15, wherein the core data is reordered prior to obtaining at least one of the different subsets of the core data.
 17. The apparatus of claim 15, wherein a transmission of a first redundancy version of the encoded data includes all of the core data, while a transmission of a second redundancy version of the encoded data includes only a subset of the core data.
 18. The apparatus of claim 15, wherein transmitting the plurality of redundancy versions of the encoded data includes: transmitting a first redundancy version of the encoded data, wherein the first redundancy version of the encoded data includes at least a first subset of the core data; and transmitting a second redundancy version of the encoded data, wherein the second redundancy version of the encoded data includes at least a second subset of the core data different from the first subset of the core data, and where the core data is reordered prior to obtaining the second subset of the core data.
 19. A method operational at a receiver, comprising: receiving a plurality of redundancy versions of encoded data, where the encoded data includes core data and non-core data, wherein each of the received redundancy versions of the encoded data includes at least a different subset of the core data; obtaining the encoded data from one or more of the plurality of redundancy versions of encoded data; and decoding the encoded data using a low-density parity check code to obtain decoded data.
 20. The method of claim 19, wherein each of the received redundancy versions of the encoded data includes sufficient core data to permit self-decodability of the encoded data.
 21. The method of claim 19, further comprising: selecting the plurality of redundancy versions from a set of redundancy versions, where the set of redundancy versions and their transmission order is pre-arranged with a transmitter.
 22. The method of claim 21, wherein each of the set of redundancy versions has a first starting point for the core data and a second starting point for the non-core data, which are provided to the receiver.
 23. The method of claim 19, wherein the encoded data is obtained by combining likelihood ratios for the received plurality of redundancy versions of the encoded data.
 24. The method of claim 19, wherein a first redundancy version of the encoded data includes all of the core data, while a second redundancy version of the encoded data includes less than all the core data.
 25. The method of claim 19, wherein the non-core data includes parity data for forward error correction.
 26. The method of claim 19, wherein the low-density parity check code uses a quasi-cyclic lifting structure, where the quasi-cyclic lifting structure is a sparse bipartite graph having a core part that is more densely populated than a non-core part.
 27. The method of claim 19, wherein receiving a plurality of redundancy versions of the encoded data includes: receiving a first redundancy version of the encoded data, wherein the first redundancy version of the encoded data includes at least a first subset of the core data; and receiving a second redundancy version of the encoded data, wherein the second redundancy version of the encoded data includes at least a second subset of the core data different from the first subset of the core data, and where the second subset of the core data is based on a reordered version of the core data relative to the first subset of the core data.
 28. The method of claim 27, further comprising: sending an indicator to retransmit the encoded data prior to receiving the second redundancy version of the encoded data.
 29. The method of claim 19, wherein receiving a plurality of redundancy versions of the encoded data further includes: receiving a third redundancy version of the encoded data, wherein the third redundancy version of the encoded data includes at least a third subset of the core data different from the first and second subsets of the core data, and the second subset and third subset of the core data is based on the same reordered core data.
 30. An apparatus, comprising: a receiver circuit for receiving a plurality of redundancy versions of encoded data, where the encoded data includes core data and non-core data, wherein each of the received redundancy versions of the encoded data includes at least a different subset of the core data; a data aggregation circuit for obtaining the encoded data from one or more of the plurality of redundancy versions of encoded data; and a decoding circuit for decoding the encoded data using a low-density parity check code to obtain decoded data. 